The present invention claims priority to Japanese Patent Application No. 2000-301411 filed on Sep. 29, 2000. The above-referenced Japanese Patent Documents is hereby incorporated by reference to the extent permitted by law.
The invention relates to a fuel cell for producing an electromotive force by reaction of a fuel, such as hydrogen, with oxygen.
As the world""s supply of fossil fuels is limited, there has been ongoing research directed toward alternative energy sources, including those that may be more environmentally friendly than traditional fossil fuels. A hydrogen gas fuel is one such example. Since hydrogen contains relatively large amounts of energy per unit weight and because it does not emit noxious gases or gases contributing to global warming, hydrogen may be an ideal energy source that is clean and moreover plentiful in supply.
Fuel cell technology involves the recovery of electrical energy from hydrogen. Fuel cell research is proceeding rapidly, with a variety of promising applications, such as large scale power generation, on-site self-generation of power, or as a power source for electric vehicles.
The fuel cell typically includes a fuel electrode, such as a hydrogen electrode, and an oxygen electrode, arranged on both sides of a proton conductor film. Supplying fuel (hydrogen) and oxygen to these electrodes induces a cell reaction that develops an electromotive force. In preparing the fuel cell, the proton conductor film, the fuel electrode and the oxygen electrode are routinely molded separately and bonded together.
However, in forming the fuel electrode and the oxygen electrode separately, a variety of inconveniences arise due to difficulties encountered in handling. For example, if the strength of the fuel electrode or the oxygen electrode is considered, a certain thickness is necessary (e.g., a thickness on the order of 100 xcexcm or more). However, if the electrode thickness is increased, the efficiency of the cell reaction is lowered, thus lowering cell performance. If, in order to avoid this, the electrode thickness is decreased, the protein conductor film can be difficult to handle separate and apart from the electrodes due to its decreased size to compensate for the decreased size of the electrodes. Thus, this can significantly lower production yield.
It is therefore an advantage of the present invention to provide a fuel cell which is easy to manufacture and superior in cell performance. Applicants have discovered that a sheet or other suitable form of a material containing carbon nano-tubes or other suitable material can be of high strength and density such that it exhibits superior and desirable current collecting characteristics. Therefore, by utilizing this sheet of material as a current collector, a high performance fuel cell can be constructed.
In an embodiment, the present invention provides for a fuel cell having a fuel electrode and an oxygen electrode in which the fuel electrode and the oxygen electrode face each other with a proton conductor disposed in-between, wherein the fuel electrode and/or the oxygen electrode include a current collector containing carbon nano-tubes or other suitable materials or combinations thereof.
The current collector containing the carbon nano-tubes is high in strength and density and, in conjunction with the high electronic conductivity of the carbon nano-tubes, exhibits superior current collection. Moreover, by employing the current collector containing carbon nano-tubes, it becomes unnecessary to consider the mechanical strength of the fuel electrode or the oxygen electrode, and hence these electrodes can be reduced in thickness. The result is that, in the fuel cell of the present invention, the cell reaction can occur efficiently to improve cell performance.
Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Invention and the figures.